The joint lawsuit led by Florida and now grouping 18 states was filed on March 23. It claims the sweeping reform of the $2.5 trillion healthcare system violates state-government rights in the U.S. Constitution and will force massive new spending on hard-pressed state governments.

"We welcome the partnership of Indiana, North Dakota, Mississippi, Nevada and Arizona as we continue fighting to protect the constitutional rights of American citizens and the sovereignty of our states,” Bill McCollum said.